Related Party Transactions (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Related Party Transaction [Line Items]
Affiliated Dealer Loan balances	$ 5.9		$ 4.9
Percentage of Affiliated Dealer Loan balances	0.30%		0.30%
New Consumer Loan assignments	1,253.6		1,152.5		786.9
Accelerated Dealer Holdback payments	(43.7)		(47.4)		(32.6)
Dealer Holdback payments	115.7		85.2		44.2
Affiliated Dealer Activity [Member]
Related Party Transaction [Line Items]
Dealer Loan revenue	1.2		1.6		3.1
New Consumer Loan assignments	3.6	[1]	1.3	[1]	3.5	[1]
Accelerated Dealer Holdback payments	0.1				0.3
Dealer Holdback payments	$ 3.2		$ 2.4		$ 1.8
% Of Consolidated [Member]
Related Party Transaction [Line Items]
Dealer Loan revenue, percentage	0.30%		0.40%		1.00%
New Consumer Loan assignments, percentage	0.30%	[1]	0.10%	[1]	0.40%	[1]
Accelerated Dealer Holdback payments, percentage	0.20%		0.10%		0.90%
Dealer Holdback payments, percentage	2.80%		2.80%		4.00%

[1] Represents advances paid to Dealers on Consumer Loans assigned under our Portfolio Program and one-time payments made to Dealers to purchase Consumer Loans assigned under our Purchase Program.